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Biomedical subjects

G Drouin

Publications and source records attributed to G Drouin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Relationships among msx gene structure and function in zebrafish and other vertebrates.

The zebrafish genome contains at least five msx homeobox genes, msxA, msxB, msxC, msxD, and the newly isolated msxE. Although these genes share structural features common to all Msx genes, phylogenetic analyses of protein sequences indicate that the msx genes from zebrafish are not orthologous to the Msx1 and Msx2 genes of mammals, birds, and amphibians. The zebrafish msxB and msxC are more closely related to each other and to the mouse Msx3. Similarly, although the combinatorial expression of the zebrafish msx genes in the embryonic dorsal neuroectoderm, visceral arches, fins, and sensory organs suggests functional similarities with the Msx genes of other vertebrates, differences in the expression patterns preclude precise assignment of orthological relationships. Distinct duplication events may have given rise to the msx genes of modern fish and other vertebrate lineages whereas many aspects of msx gene functions during embryonic development have been preserved.

Amino Acid Sequence↗
PubMed1996

Nutritional factors and prostate cancer: a case-control study of French Canadians in Montreal, Canada.

The relationship between the risk of prostate cancer and dietary intake of energy, fat, vitamin A, and other nutrients was investigated in a case-control study conducted in Montreal (Quebec), Canada. French Canadians aged 35 to 84 years with a recent, histologically confirmed diagnosis of adenocarcinoma of the prostate were identified through the admission offices of five major francophone teaching-hospitals in Montreal from 1989 to 1993. Population-based controls matched for age (+/- five years), language, and place of residence were selected by a modified random-digit dialing method. The study included 232 cases and 231 controls. Information on dietary intake was collected by means of a quantitative dietary history. No association was evident between energy intake and the risk of prostate cancer. In contrast, there was some evidence of an inverse association with intake of total fat, animal fat, monounsaturated fat, and particularly saturated fat (odds ratio = 0.69, 95 percent confidence interval = 0.40-1.18, P = 0.05), while a nonsignificant positive association was found with polyunsaturated fat. In addition, high intake of retinol and vegetable protein (highest cf lowest quartile) was associated with reduced risk, but was not statistically significant. No associations were established between intake of other nutrients and risk. These patterns persisted after adjustment for a number of potential confounding factors.

Adenocarcinoma↗
PubMed1996

Phylogeny and substitution rates of angiosperm actin genes.

Forty-four actin genes from five angiosperm species were PCR-amplified, cloned, and sequenced. Phylogenetic analysis of 34 of these actins, along with those previously published, indicates that angiosperm actin genes are monophyletic and underwent several duplications during evolution. Orthologues have been identified between Solanaceae species, as well as between Solanaceae species and soybean. These sequences were used to calculate nucleotide substitution rates. The synonymous rate (6.96 x 10(-9) substitutions/site/year) is similar to that of other nuclear protein-coding genes, but the nonsynonymous rate (0.19 x 10(-9) substitutions/site/year) is 6-19 times higher than that of mammalian actin genes. Relative rate tests indicate that actin genes are evolving at similar rates in monocots and in dicots. Evidence is also presented that some members of the maize actin multigene family have been involved in gene conversion events, that the potato genome contains 24 +/- 12 actin genes, and that potato and tomato diverged 11.6 +/- 3.6 MYA.

Actins↗
PubMed1995

Trapping gel electrophoresis of end-labeled DNA: an analytical model for mobility and diffusion.

As shown by Ulanovsky, Drouin and Gilbert (Nature 1990, 343, 190-192), the gel electrophoretic migration of DNA is severely reduced by steric trapping when streptavidin is attached to one end of the polyelectrolyte. We present a model that allows us to calculate both the mobility and the diffusion coefficient, hence the resolution factor of the resulting separation. We compare our results to those of Défontaines and Viovy (Electrophoresis 1993, 14, 8-17) and we show that the averages over the molecular conformations must be done carefully. We also show that trapping increases diffusion substantially and that this makes constant-field trapping electrophoresis incapable of increasing the number of bases read per sequencing run. Finally, we conclude that severe trapping may lead to highly anomalous transport behavior where one cannot define a velocity or a diffusion constant.

Bacterial Proteins↗
PubMed1995

The Giardia lamblia actin gene and the phylogeny of eukaryotes.

The single-copy actin gene of Giardia lamblia lacks introns; it has an average of 58% amino acid identity with the actin of other species; and 49 of its amino acids can be aligned with the amino acids of a consensus sequence of heat shock protein 70. Analysis of the potential RNA secondary structure in the transcribed region of the G. lamblia actin gene and of the single-copy actin gene of nine other species did not reveal any conserved structures. The G. lamblia actin sequence was used to root the phylogenetic trees based on 65 actin protein sequences from 43 species. This tree is congruent with small-subunit rRNA trees in that it shows that oomycetes are not related to higher fungi; that kineto-platid protozoans, green plants, fungi and animals are monophyletic groups; and that the animal and fungal lineages share a more recent common ancestor than either does with the plant lineage. In contrast to small-subunit rRNA trees, this tree shows that slime molds diverged after the plant lineage. The slower rate of evolution of actin genes of slime molds relative to those of plants, fungi, and animals species might be responsible for this incongruent branching.

Actins↗
PubMed1995

Genetic map of rat chromosome 5 including the fatty (fa) locus.

Thirteen loci, including the obesity gene fatty (fa), were incorporated into a linkage map of rat Chromosome (Chr) 5. These loci were mapped in obese (fa/fa) progeny of a cross between BN x 13M-fal+F1 animals. Obese rats were scored for BN and 13M alleles at four loci (Ifna, D1S85h, C8b, and Lck1) by restriction fragment length polymorphisms and at eight additional loci (Glut1, Sv4j2, R251, R735, R980, R252, R371, and R1138) by simple sequence length polymorphisms (SSLP). The resulting map spans 67.3 cM of Chr5, presenting nine previously unmapped loci and one locus (Lck1) previously assigned to Chr 5 by use of somatic cell hybrid lines. Seven of the eight SSLP loci are newly identified; the SSLP linkage group alone spans 56.8 cM. The order of the loci is Sv4j2-R251-R735-R980-R1138-Ifna-fa-+ ++D1S85h-C8b-(Glut1-R252-R371)-Lck1. One locus, D1S85h, was found to lie only 0.4 cM from fa, close enough to serve as a reliable marker for the prediction of phenotype from genotype, and will be useful also for studies on the development of obesity in the fatty rat.

Alleles↗
PubMed1995

The concerted evolution of 5S ribosomal genes linked to the repeat units of other multigene families.

We review all instances in which the nuclear 5S rRNA genes of fungi, protist, nematode, and arthropod species have been reported to be linked to the tandemly repeated units of the rDNA, trans-spliced leader, and histone multigene families. The evolution of these gene arrangements is analyzed by mapping them to independently derived phylogenies. These analyses show that 5S rRNA genes have repeatedly become linked to diverse tandemly repeated gene families and that such linkages have also been subsequently inverted or lost in some species. These variable gene linkages are probably the result of stochastic gains and losses of variant repeat units, where functional 5S rRNA had transposed, by the mechanisms which are responsible for the concerted evolution of tandemly repeated multigene families. We discuss the possible mechanisms of 5S rRNA gene transposition and suggest that the characteristics of their promoter elements, transcription, and termination signals may allow functional copies of these genes to be fortuitously transposed through an RNA intermediate. We also review the evidence which shows that the linked 5S rRNA gene copies are transcribed. We conclude that the observed patterns of 5S rRNA gene linkages to the repeat units of other tandemly repeated multigene families have likely arisen due to fortuitous recombination events and are unlikely to represent the remnants of an eubacterial-like arrangement of rDNA operons or to have been established due to selective pressures.

Biological Evolution↗
PubMed1995

Design methodology for a multifunctional hand prosthesis.

The first part of this paper reviews different approaches to define the motion of the fingers and the thumb in order to obtain prehension. The last part presents the design of a hand prosthesis based on a new plane of action for the thumb and on proposed design specifications and functional characteristics. The design methodology consists of two steps: the morphology design of the hand prosthesis and the 4-bar mechanism design for each finger. A 3-D computer-aided design (CAD) interactive program was used as a design tool to obtain the hand morphology. This CAD technique was also used to check the geometry, the relative motions of the fingers, and the possibility of interference for the proposed model with two prehension patterns (tridigital and lateral). It is noted that identical flexion angles of the finger joints were obtained for these two prehension patterns, the difference being in the inclination angle of the thumb's plane of flexion. This finding greatly simplified the design of the internal mechanisms of the fingers. CAD was a powerful tool in the design process of this hand prosthesis and will be more and more useful in the future.

Artificial Limbs↗
PubMed1994

Simulation of reduced band broadening during single-stranded DNA pulsed field electrophoresis in polyacrylamide gels.

Using a computer simulation algorithm based on the reptation model, we investigated the effects of pulsed field gel electrophoresis on the separation of single-stranded DNA molecules in denaturing polyacrylamide gels. Pulsed fields that combine two different field intensities were found to affect the orientation of the reptation tube as well as the electrophoretic velocity, the rate of band broadening, the plate height and the molecular length for which the minimum of mobility was found, in agreement with available experimental results. Due to "memory" effects, pulses alternating between the forward and backward directions can reduce the diffusion constant by many orders of magnitude. Pulses of identical polarity but different intensities reduce the diffusion because stretches of less-oriented DNA segments are conserved during the migration. We suggest that, for DNA sequencing, pulsed fields of fixed polarity should be used to reduce band broadening and not to overcome band inversion or suppress molecular orientation. We conclude that, using a low intensity, constant electric field will lead to smaller band widths than any pulsed field regime, in a similar length of experimental time, but with less complications.

Algorithms↗
PubMed1994

The biased reptation model of DNA gel electrophoresis: a user guide for constant field mobilities.

The biased reptation model of DNA gel electrophoresis is simple enough to allow one to obtain detailed analytical and numerical predictions for experimentally relevant situations. Although it is not always applicable for explaining experimental results, the biased reptation model is usually a good starting point for data analysis. Unfortunately, the model is often reported as being incapable of explaining experimental data because the users have not analyzed the data properly or because they attempted to use the model outside its expected range of applicability. This article presents a detailed practical guide to the model and its limitations, as well as a complete description of its predictions regarding the analysis of constant field mobilities.

DNA↗
PubMed1994

Effect of plasma treatment on tribological properties of synthetic ligaments.

The objective of this study was to determine the optimal experimental conditions for plasma treatment of polyester ligaments. Two different surface modification techniques were used: tetrafluoroethylene and methane. Gas flow rate, pressure, power, and treatment period giving a thin film with low friction coefficient and low surface energy was determined. Control and plasma treated surfaces were characterized by X-ray photoelectron spectroscopy to investigate the functionalization of the treated surfaces in detail. The surface tension of control and plasma treated surfaces were determined from contact angle measurements to understand the adhesion and reactivity of films with aqueous medium. The results showed a decrease in friction coefficient from 0.45 to 0.28 and from 0.45 to 0.26 for thin films deposited respectively by tetrafluoroethylene (TFE) and methane (CH4) plasma. Contact angles increased from 63 degrees to 120 degrees for TFE plasma and from 63 degrees to 93 degrees for CH4 plasma. Large contact angles mean a weak affinity between molecules in water/material phase, so that the power to attract cells to the surface of the material is too weak. The results showed that optimal film, i.e., low static friction coefficient and large contact angle, can be obtained by a CH4 plasma treatment at high power RF. For TFE plasma treatments, a low power RF is needed to obtain a thin film with a stable chemical structure.

Adhesiveness↗
PubMed1993

On the limits of near-equilibrium DNA gel electrophoretic sequencing.

High field intensities deeply affect the migration mechanisms of DNA in gels. The corresponding large electric forces lead to far-from-equilibrium transport properties such as the limiting mobility, increased diffusion and strong pulsed field responses. We present a theoretical study of the conditions required to retain a near-equilibrium reptation transport behaviour. We then examine the possibility of increasing both the field intensity and the gel concentration to sequence large single-stranded DNA molecules rapidly and efficiently. Finally, we discuss possible experimental approaches based on our theoretical predictions.

Base Sequence↗
PubMed1993

The irradiation effect on the initial mechanical properties of meniscal grafts.

In this study, the effect of sterilization was investigated on the mechanical properties of rabbit's meniscal grafts. The processes of freezing and irradiation were carried out and their effects upon the elastic and viscoelastic properties measured using a tensile testing machine and an indentation test. It was found that gamma irradiation, at dosages commonly used for sterilizing grafts, had a significant adverse influence on the elastic and viscous response of the grafts. Freezing led also to a small significant decrease in elastic stiffness but no change in failure strength. It is concluded that irradiation sterilization is unsuitable for clinical use and other techniques should be used whenever possible.

Animals↗
PubMed1993

Exact behaviour of single-stranded DNA electrophoretic mobilities in polyacrylamide gels.

We demonstrate the existence of a gel edge effect where the velocity of the samples varies in the first and last centimetres of the gel. In spite of this effect, a differential method of velocity determination leads to exact mobility data. Further analysis against DNA length N and electric field E shows that the molecules always migrate according to an A/N+B(E) law, except in a limited range of E and N, whereas a 1/N1.6 entropic driven regime is found. Below a threshold electric field intensity B(E) varies as E2, in good agreement with the biased reptation mechanism, while at stronger electric fields intensities, B(E) stays constant. This second mechanism is not described by any actual theory, but might be attributed to a geometration-like mechanism. Implications of our findings in sequencing electrophoresis are discussed.

DNA, Single-Stranded↗
PubMed1992

Why can we not sequence thousands of DNA bases on a polyacrylamide gel?

Pulsed fields have been remarkably useful at extending the range of DNA molecular sizes that can be separated on agarose gels by controlling the field-induced molecular orientation that often limits the resolution of large molecules. Unfortunately, the same approach seems to be much less effective for DNA sequencing on polyacrylamide gels. We present an experimental and theoretical (modelling) study of DNA sequencing which shows that molecular orientation is indeed not the main limiting factor for sequencing devices that use moderate field intensities and polyacrylamide as a separating matrix. We examine the interplay between electric field intensity, molecular size and resolution, and we suggest different approaches to increase the resolution limit of standard and automated sequencing gels. The theoretical limits of high-field electrophoretic sequencing are also discussed. We conclude that new ideas will be needed to go beyond one kilobase.

Acrylic Resins↗
PubMed1992

Evaluation of metallic personalized hemiarthroplasty: a canine patellofemoral model.

The purpose of this study was to characterize the response of articular cartilage to weight bearing against a metallic personalized hemiarthroplasty prosthesis. Ten dogs each underwent surgery in which an elastomeric replica of the left femoral patellar groove was made. Using this replica, a 0.5-mm-thick prosthesis was cast in Co-Cr alloy and subsequently the surface was polished to a mirror finish which had a center line average roughness value in the range of human hemiarthroplasty implants. A second surgery was performed to resurface the left trochlea with this prosthesis. Five animals were sacrificed at 3 months and 5 at 6 months. Cartilage damage occurred primarily in the distal region of the patella, and was especially evident at 6 months. Mechanical indentation tests conducted on patellar cartilage in a saline bath at 37 degrees C indicated both increased deformation and residual deformation in the affected areas, indicative of degenerative change. Areas of fibrillation with a depletion of proteoglycans were identified histologically. These areas were only superficial at 3 months but became more extensive at 6 months. Rheological analysis of the synovial fluid of tests joints indicated that a decrease in viscosity occurred from 3 to 6 months, an additional indicator of progressive degeneration. This novel implant model showed that even if a metallic hemiarthroplasty implant had an identical geometry as the joint surface being replaced and had a reasonably smooth surface, cartilage degeneration inevitably resulted.

Animals↗